Effects Of Polystyrene Microplastics On The Microbiota And Metabolism In Zebrafish

With the widespread use of plastic products in recent years,microplastics(MPs)have become a common contaminant in environment.At present,the potential toxic effects of MPs on aquatic organisms have been confirmed.However,there are few reports on the effects of MPs on the gut microbiota and metabolism of organisms.In this study,both larval zebrafish and adult zebrafish were exposed to different concentrations and different size of polystyrene microplastics(PS-MPs)to study the effects on gut microbiota and metabolism in larval zebrafish,and developmental toxicity to larval zebrafish,as well as the physiological toxicity to adult zebrafish.First,in order to analyze the effects of PS-MPs on microbiota and metabolism in larval zebrafish,we exposed zebrafish embryos to 5-and 50-?m PS-MPs for 7 days.The results showed that PS-MPs not only changed the abundance of some microorganisms at the "phylum" level and "genus" level,but also reduced the diversity of microbiota.In terms of metabolism,GC/MS result showed that PS-MPs caused significant changes in the metabolic profile of zebrafish.Among them,the contents of 78 metabolites changed after exposure to 5-?m PS-MPs,while a total of 121 metabolites changed after exposure to 50-?m PS-MPs.These altered metabolites included carbohydrates,fatty acids,amino acids,nucleic acids,and so on.After further analysis,these differential metabolites were involved in energy metabolism,glycolipid metabolism,inflammatory response,neurotoxicity,nucleic acid metabolism and oxidative stress.PS-MPs also significantly altered the transcription levels of glycolipid-related genes such as HK1,ACO,and DGAT2.These results indicated that PS-MPs could significantly alter the composition of gut microbiota and cause metabolism disorder in zebrafish.Secondly,in order to explore the developmental toxicity of PS-MPs on larval zebrafish,we further examined the relevant indicators which related to swimming behavior,neurodevelopment,immune response and oxidative stress.The results showed that 5-and 50-?m PS-MPs affected the swimming behavior of larval zebrafish,and significantly inhibited the activity of AchE and the level of DA.In addition,the transcription levels of neurodevelopmental-related gens such as Gfap,Shha,Elavl3 and Gap43 also decreased after PS-MPs exposure.Furthermore,PS-MPs also significantly up-regulated the levels of some pro-inflammatory factors and the transcription levels of genes.Otherwise,PS-MPs significantly down-regulated the levels of IL-10 and C3 and transcription levels of genes in larval zebrafish.Finally,in order to study the physiological toxicity of PS-MPs on adult zebrafish,we further examined the body weight,body length and fatness of adult zebrafish,and detected the transcription levels of glycolipid metabolism-related genes and related biochemical indicators in the liver of adult zebrafish.The results showed that 0.5-and 5-?m PS-MPs significantly affected the normal growth of adult zebrafish,which was manifested by a significant decrease in body weight and fatness.In addition,PS-MPs significantly changed the transcription levels of glycolipid metabolism-related genes such as HK1,PK,PEPCK,ACO,CPT1,and ACC1,and influenced the activities of ?-ketoglutarate dehydrogenase and isocitrate dehydrogenase.In addition,PS-MPs significantly changed the levels of glucose and TG in liver.These results indicated that PS-MPs may affect the normal growth and glycolipid metabolism,indicating potential physiological toxicity to adult zebrafish.Overall,our results indicated that PS-MPs not only caused the microbiota dysbiosis and hetapic metabolism disorder,but also induced developmental toxicity such as neurotoxicity,immunotoxicity,and oxidative damage in larval zebrafish.It also caused physiological changes to adult fish by affecting the growth of adult fish and hepatic metabolism.