Study On The Toxicity Of Polystyrene Nanoplastics On Zebrafish

In the present time,plastic pollution has attracted more and more attention due to the large-scale production and use of plastic products in human life.The plastic in the natural environment can be decomposed into microplastics(MPs)smaller than 5 mm and nanoplastics(NPs)with diameters between 1-100 nm with the action of physics,chemistry and biology.Nanoplastics can not only adsorb organic pollutants in the environment,but also can enter the organism through the cell membrane and accumulate in tissues and organs,resulting in a series of toxic effects on the organisms.However,until now little is known about its distribution,bioaccumulation,and toxic effects on the organisms.Therefore,this study aimed to evaluate the embryonic developmental toxicity and acute toxicity of the fluorescent polystyrene(PS)nanoplastics(50 nm in diameter)on zebrafish.Using the immersion method,the embryos were exposed to 0,0.1,1 and 10 mg/L of nanoplastics solutions respectively,and the adult zebrafish were intraperitoneally injected with 0 ?g/ kg or 250 ?g/ kg nanoplastics solutions.The distribution of nanoplastics,embryonic development,oxidative stress,and inflammation in the fish were determined.The main results are as follows:(1)After the embryos were exposed to various concentrations of nano-plastics,it was found that the nanoplastics could penetrate the chorion and skin into zebrafish embryos and larvae,fluorescent nanoplastics were observed in zebrafish embryos from 24 h.Meanwhile,fluorescence intensity of zebrafish embryos increased gradually with concentration increase and the development stage of embryos.(2)After exposure to various concentrations of nanoplastics,there was no significant change in embryo mortality and malformation rate between the treatment groups and the control group.The hatchability of embryos in 1 mg/L and 10 mg/L treatment groups decreased significantly at 48 h when compared with the control group,but no difference was found at 96 h.In addition,the heart rate of zebrafish embryos in treatment groups decreased significantly at 72 h compared with the control group.(3)The expression of antioxidant related genes and enzyme activity in zebrafish embryos were detected after the embryos were exposed to different concentrations of nanoplastics.The result showed that the relative expression level and activity of superoxide dismutase(SOD)were increased in all treatment groups compared to that of the control group.The activity of catalase(CAT)in 10 mg/L treatment group also increased significantly at 72 h and 96 h.(4)The expression of immune related genes interleukin-1-?(IL-1?),interleukin-6(IL-6),interleukin-8(IL-8),interleukin-10(IL-10),interferon-?(IFN-?),and tumor immune factor(TNF-?)were detected by q PCR after zebrafish embryos were exposed to different concentrations of nanoplastics.The result showed that the relative expressional levels of IL-1 ?,IL-6,TNF-?,and INF-? were significantly upregulated,while IL-10 decreased at first and then increased,when compared to the control group.The contents of IL-1?,IL-6,and TNF-? were detected by ELISA and the result showed that the change tendency of IL-1 ?,IL-6,and TNF-? levels shared the similar pattern to the gene expression.(5)The result of histological observation showed that the hepatic sinusoids enlarged and liver inflammatory cells infiltrated in the liver of the treatment fish after intraperitoneal injection of 250 ?g/ kg of nanoplastics into adult fish at 24 h and 48 h,suggesting that the injury of liver was induced by the nanoplastics.(6)The expressions of nuclear factor erythroid-2 related factor 2(Nrf2),Kelch-like ECH-associated protein 1(Keap1),SOD,and CAT in zebrafish liver were detected by q PCR after intraperitoneal injection of nanoplastics into adult fish.The result showed that the expression of Nrf2 significantly increased,but Keap1 was significantly decreased.In addition,the expression and vitality of SOD and CAT also increased correspondingly.(7)The expression of immune related factors was detected by q PCR in the liver of adult fish following intraperitoneal exposure to nanoplastics,and the contents of IL-1?,IL-6 and TNF-? were also detected by ELISA.The result showed that the contents of IL-1?,IL-6,and IL-8 were basically consistent with the changes of their gene expressions showing an increasing trend,that is,the relative expression of IL-10 and TNF-? increased significantly,but the expression of INF-? was first up-regulated but then downregulated.These results indicated that nanoplastics could enter into zebrafish embryo and adult tissues,inducing the change of zebrafish liver structure,oxidative stress,and inflammatory reaction in the fish liver,and affecting the growth and development of zebrafish.This study might provide an experimental basis for the toxicology of nanoplastics in aquatic organisms.