Atrazine And Its Main Metabolites Exposure Induce The Neurotoxicity And Immunotoxicity In Larval Zebrafish (Danio Rerio)

Atrazine?ATZ?and its main chlorometabolites,i.e.,diaminochlorotriazine?DACT?,deisopropylatrazine?DIP?,and deethylatrazine?DE?,have been widely observed in aquatic systems near agricultural fields.However,the people usually pay more attention to the effects of ATZ,the possible effects of its metabolites on aquatic animals are still not arouse concerns.In this study,we analyzed the developmental toxicity,neurotoxicity and immunotoxicity,after 5 days of exposure to 30,100,300?g L^-1 ATZ and its main chlorometabolites,The mian results were observed as follows:1)It was observed that several developmental endpoints such as the heartbeat,bodylength,and morphological abnormalities were influenced by ATZ and its metabolites in early developmental stages of zebrafish,and the high concentration of the metabolites even resulted in developmental malformation in larval zebrafish.2)The swimming behaviors of larval zebrafish were significantly disturbed,after 5 days of exposure to the middle and high concentration of ATZ and its main chlorometabolites.Correspondingly,the acetylcholinesterase?AChE?activities were consistently inhibited in larval zebrafish.It was also observed that ATZ and its main chlorometabolites were neuroendocrine disruptors that could impact the expression of neurotoxicity-related genes such as Ache,Gap43,Gfap,Syn2a,Shha,Mbp,Elavl3,Nestin and Ngn1 in early developmental stages of zebrafish.According to our results,it was possible that not only ATZ but also its metabolites?DACT,DIP and DE?had the same or even more toxic effects on different endpoints of the early developmental stages of zebrafish.3)ATZ and its metabolites exposure could also induce immunotoxicity in the early developmental stages of zebrafish.Firstly,after 5 days of exposure to 30,100,300?g L^-1 ATZ and its main chlorometabolites,we found that the transcription status of some immune-related genes e.g.:Tnfa,Ifn,I?-1b,Il-6,Il-8,Cxcl-clc,Cc-chem,C3 and the expression levels of protein TNFa,IFN,IL-6,IL-8 were up-regulated,indicating that ATZ and its metabolites caused immunotoxicity in larval zebrafish;Secondly,the larval zebrafish were pretreated with ATZ and its metabolites and then treated with 12.5?g mL^-1 LPS or 10⁷ dead E.coli for 12 h,the immune responses was also significantly,affected especially for the effects of high concentration of DACT,DIP and DE.Thirdly,after exposure to ATZ and its main metabolites,the larval zebrafish were treated with substrate BAPNA for 1h,we obaseved that the mast cell and tryptase levels in the water,the expression of immune-related genes and protein in the larval zebrafish were also signicantly change.And the DACT had more immunotoxicity than DIP,DE,and ATZ.Taken together,ATZ existed in the real environment not only in the form of the original compound;It could be degraded or metabolized to several different products.According to our results,not only ATZ but also its metabolites such as DACT,DIP and DE may also have the same or more toxic effects on zebrafish.We believe that the information presented in this study is helpful to understand the mechanism of ATZ-and its metabolites-induced toxicity in zebrafish..