Toxic Effects Of Florasulam On Adult Zebrafish And Embryo

Florasulam is a new herbicide developed by Dow Agrochemical Co.,LTD.It is mainly used to control weeds in wheat,barley and corn fields.Due to its low cost and good control effect,florasulam has been widely used in the world.But with florasulam to promote the use of large area,inevitably cause its residue in water environment,and pesticides in water environment medium easy to cause biological enrichment phenomenon,for individuals and even the entire aquatic ecosystems caused serious harm,the florasulam was very scarce ecological toxicology to aquatic organisms.Therefore,this study took zebrafish as the indicator organism to explore the toxic effects of florasulam on adult zebrafish and embryos.The level of pesticides in the environment determines the biological exposure dose,so this test is to florasulam residues in water environment as the basis,research different concentrations(0.1 and 1?g/L)of florasulam on the acute toxicity of zebrafish and 14 and 28 days and embryonic zebrafish fish exposed after 120 hours exposure and chronic toxicity effect.In this study,the contents of reactive oxygen species(ROS),the activity of superoxide dismutase(SOD)and catalase(CAT)in zebrafish liver and embryo were determined,Glutathione s-transferase(GST)activity, glutathione peroxidase(GSH-Px)activity and malondialdehyde(MDA)content to evaluate the oxidative stress effect of florasulam on adult zebrafish and embryos.DNA damage of adult zebrafish and embryos was evaluated by measuring the content of 8- hydroxydeoxyguanosine(8-OHd G)in liver and embryo of zebrafish.Six genes related to cell apoptosis,p53 gene,B-cell lymphoma-2 gene,(Bcl-2),Bcl-2-associated X protein(Bax),and cysteinyl aspartate specific proteinase containing cysteine and the expression levels of Caspase-3,Caspase-8 and Caspase-9 genes in the Caspase family were studied to explore the effects of florasulam on apoptosis of adult zebrafish and embryonic cells.This study has guiding significance for evaluating the ecotoxicity and genotoxicity of florasulam.The main results of this study are as follows:(1)The median lethal concentration(LC₅₀)at 96 hours of acute toxicity to adult fish and embryo was greater than 100 mg/L,and the toxicity of florasulam to zebrafish was low.(2)Compared with SC,ROS content in adult zebrafish significantly increased at 14 and28 days after florasulam exposure,and excessive ROS would affect SOD,CAT and GST activities in zebrafish.The activities of SOD,CAT and GST in 0.1?g/L treatment group were all activated on the 14th and 28th day,indicating that florasulam can cause oxidative stress in zebrafish.At the 14th and 28th day,MDA content in 0.1?g/L and 1?g/L treatment groups increased significantly,and there was a dose-effect relationship with the increase of exposure concentration.This is because the increase of ROS leads to the accumulation of MDA in the body,resulting in lipid peroxidation damage.At the 14th and 28th day,the 8-OHd G content in 0.1?g/L and 1?g/L treatment groups was significantly higher than that in SC control group,which also reflected that florasulam caused certain DNA damage to zebrafish.(3)ROS content in zebrafish embryos showed an upward trend after 120 hours of florasulam exposure,and ROS content in 0.1?g/L and 1?g/L treatment groups was significantly increased compared with the control group,which indicated that ROS accumulation occurred in embryos.The activities of SOD and CAT in antioxidant enzymes increased with the increase of florasulam exposure concentration,presenting a dose- response relationship.The activity of GSH-Px in zebrafish embryos was significantly different between the 1?g/L treatment group and the SC treatment group,this indicated that florasulam caused oxidative stress on zebrafish embryos.MDA content increased with the increase of exposure concentration,and there was a significant difference between 1?g/L treatment group and SC,indicating that lipid peroxidation damage occurred in zebrafish embryos.Different from adult fish,there was no significant difference in the content of 8-OHd G in embryos during the whole process of exposure,indicating that florasulam did not cause DNA damage to embryos.(4)The gene expression of adult zebrafish was affected to some extent by florasulam exposure,and p53 gene expression was up-regulated in 0.1?g/L treatment group on day 28.Bcl-2/Bax ratio decreased in 0.1?g/L and 1?g/L treatment groups at day 14 and 28, indicating that apoptosis was promoted in the body.On day 28,the expressions of Caspase-3,Caspase-8 and Caspase-9 genes were down-regulated in 0.1?g/L and 1?g/L treatment groups,suggesting that florasulam exposure could inhibit cell apoptosis and easily induce cell carcinogenesis.(5)The gene expression of zebrafish embryos was affected to some extent after 120hours of florasulam exposure,and the Bcl-2/Bax ratio in the 1?g/L treatment group was significantly increased,indicating that exogenous pollutant caused certain damage to the body,inhibited the apoptosis of the body cells,and easily induced the carcinogenesis of cells.The expression levels of p53,Caspase-3,Caspase-8 and Caspase-9 genes were up-regulated in 0.1?g/L and 1?g/L exposure groups,suggesting that in order to reduce the effects of florasulam,apoptosis was promoted in the body to remove some carcinogenic cells.(6)The Integrated Biomarker Response index(IBR)was calculated,and the toxicity of florasulam exposure to adult zebrafish increased with the increase of exposure concentration,and the toxicity was lower in 0.1?g/L treatment group than in 1?g/L treatment group.The toxicity decreased with the increase of exposure time,toxicity ranged from 14 days to 28 days.MDA and 8-OHd G were more sensitive to pollutants in adult zebrafish.The toxicity of florasulam exposure to zebrafish embryos increased with the increase of exposure concentration,the toxicity of 0.1?g/L treatment group was less than 1?g/L treatment group,and the more sensitive index in embryos was p53 gene.Therefore,when evaluating the effects of florasulam on adult zebrafish and embryos,we should first pay attention to the sensitive indicators of MDA,8-OHd G and p53 genes.