Stress Mechanism Of Triclocarban Exposure Induced Neurotoxicity And Immunotoxicity In Zebrafish

Triclocarban（TCC）is a broad-spectrum,highly effective antimicrobial agent in pharmaceuticals and personal care products（PPCPs）.High concentrations of TCC were detected in different environmental media and various organisms.It has been listed as one of the top ten most common water pollutants with toxic effects on a variety of organisms.In this study,the spinal model organism zebrafish（Danio rerio）was used as the exposure object,and the neurotoxicity and immunotoxicity of acute and chronic exposure to TCC on zebrafish embryos,larvae and adults were systematically investigated.Furthermore,the genotoxicity of TCC to the offspring（F₁）larvae of chronically exposed adult fish and its mechanism were explored.Through the research,the following conclusions are drawn:（1）Under acute exposure to TCC,the results of transcriptome sequencing showed that differentially expressed genes were mainly enriched in functions and pathways such as neural,immune,reproductive,redox and cancer.Acute exposure to TCC caused excessive neuronal apoptosis,neuronal developmental defects,and abnormal lateral line neuromast structure in larval zebrafish.TCC led to a concentration gradient-dependent decrease in voluntary movement activity of embryos and larvae,a decrease in sensitivity to acoustic stimulation,and a disturbance of light-dark rhythm.It alters the expression levels of neural and immune marker genes in larval zebrafish,producing toxic effects at the molecular level.（2）Chronic exposure to TCC resulted in a decrease in the BMI index of zebrafish,a shorter body width,a significant contraction of the abdomen of female fish,and curvature of the spine in some of the zebrafish.It causes zebrafish adults to tend to a quiet environment,decrease startle response,risk aversion and color discrimination,reduce social willingness,and impair learning,memory,discrimination and cognitive functions.In zebrafish,TCC induced a decrease in the abundance of intestinal flora,uneven distribution,and changes in the composition of the colony at various levels such as phylum and class.The Alpha diversity was reduced,and the Beta diversity was significantly different from the control group.It causes damage to the gut,gill filaments and brain tissue of adult zebrafish,and damage to the gut-brain axis.Both sodium deoxycholate（SDA）and vitamin C（VC）had a certain rescue effect on adult zebrafish exposed to TCC.（3）Chronic exposure to TCC resulted in decreased GSI,cumulative egg production,and embryo quality in P₀ zebrafish,as well as a certain degree of damage to the gonads of both female and male fish.The brain and head kidney of the F₁generation larvae bred from the P₀ generation zebrafish that were chronically exposed to TCC showed excessive apoptosis,abnormal neuromast development,decreased voluntary movement activity,and decreased sensitivity to sound and light stimulation.The above phenomenon indicated that TCC produced a significant genotoxic effect.（4）circ SGOL1 has a ring-like characteristic and is co-expressed in sperm,egg and2-cell stage.It can be inherited to the F₁ generation through TCC exposed parents and its expression is up-regulated in the F₁ generation.Artificial in vivo intervention of circ SGOL1 overexpression induced a large number of deformities in zebrafish and resulted in apoptosis.Circ SGOL1 can bind to the downstream hn RNP A1 protein,artificially interfere with the knockdown of hn RNP A1 protein in vivo,and induce a large number of deformities in zebrafish.hn RNP A1 protein induces zebrafish apoptosis by acting on the downstream apoptosis marker genes of Bax,Bcl2 and Caspase3.In conclusion,TCC-exposed parent induces apoptosis in F₁ generation by up-regulating circ SGOL1 targeting hn RNP A1 protein and acting on downstream apoptosis marker genes,which clarifies the mechanism of TCC-induced apoptosis.