Effect On Histological Structure,oxidative Stress And Apoptosis In Brain And Liver Of Zebrafish By Triazophos Exposure

Triazophos is a widely used organophosphorus pesticide for controlling agricultural pests.The extensive application of triazophos results in its residue in agricultural products and in the environment which has become a big concern now.The drug as a nerve agent,the effect on land animals has been studied in a lot of literature,however,little attention was paid to the effect of triazophos exposure on hitological structure,oxidative stress and apoptosis of fish.In this study,adult zebrafish(Danio rerio)was exposed to triazophos at different concentrations(0.06,0.3 and 1.5mg/L)for 96 h in vitro to observe the change of histological structure of brain and liver in zebrafish,the ROS level,SOD and CAT activity,GSH and MDA content,the activity of caspase3 and caspase9,and mRNA expression of genes related to oxidative stress and apoptosis(Sod1,Sod2,Cat and Gpx;Apaf-1,P53,Bax,Bcl2,Caspase3 and Caspase9).The main results of the present study were listed below:1.Effect of triazophos on histological structure of cerebellum and liver in zebrafishIn histological level,the molecular and granular layers of cerebellum showed vacuolar structure after 96 h treatment of zebrafish with triazophos,and a large number of nuclear retraction,tissue vacuolation,cytoplasmic loss were observed in liver.From the fine structure level,the mitochondrial vacuolation and membrane damage of brain cells were found,and the cristae of mitochondria disintegrated partly in hepatocytes.2.Effect of triazophos on oxidative stress in zebrafishCompared with the control,ROS content showed an upward trend in brain and liver of zebrafish after exposure to triazophos.In brain,SOD and CAT activity,and GSH content increased after exposure;SOD and CAT activity in liver increased at 24 h and decreased at48 h,and then increased at 96 h,and GSH content showed a trend of first increased and then decreased.These above change indicated that the antioxidant system of zebrafish was affected by triazophos exposure.In brain,Sod1,Sod2 and Cat gene showed a trend of increasing,follwed decreasing,while Gpx gene increased in all points.In liver,Sod1,Sod2 and Cat gene showed a trend of decreasing at 24 h and increasing at 48 h,and then decreasing at 96 h,while Gpx gene showed a trend of increasing,then decreasing and then increasing in mentioned points.The above results showed that triazophos caused oxidative stress in the brain and liver of zebrafish.Also,we found MDA content increased after triazophos exposure,which indicated lipid peroxidation was caused by triazophos in zebrafish.3.Effect of triazophos on apoptosis in zebrafishAfter triazophos exposure,mitochondrial membrane potential showed a downward trend in the brain and liver of zebrafish and the activity of caspase3 and caspase9 increased after 96 h exposure with a concentration-dependent manner.In brain,the expression of genes Caspase3,Caspase9 and Apaf-1 showed a trend of down-regulated and then up-regulated,Bax and P53 were up-regulated,and Bcl2 was up-regulated and then down-regulated.In liver,Caspase3 was down-regulated,Caspase9 was down-regulated,then up-regulated,and then down-regulated,Bax and P53 were down-regulated and then up-regulated,Bcl2 and Apaf-1were up-regulated and then down-regulated.These results indicated that triazophos exposure lead to apoptosis in zebrafish and it was speculated that the apoptosis may occur through mitochondrial apoptosis.In summary,the study confirmed that triazophos can damage histological structure of cerebellum and liver tissues,cause oxidative stress and cell apoptosis,which is benifical for further research on toxic mechanism of triazophos to aquatic organisms.