Study On Toxic Effects Upon The Intestinal And Hepatocyte By Exposure To Polystyrene Microplastics And Tetracycline

Microplastics(MPs)and tetracycline are both emerging environmental pollutants that enter organisms through the food chain,and thus give rise to an increasing concern of threating human health.Due to the characteristics of microplastics,such as adsorption and large specific surface areas,they inevitably interact with tetracycline in the environment.However,the toxic impacts of their single and co-exposure have not well been recognized on the body.As the largest contact interface between humans and the environment,the intestinal is the first organ that responds to invasive substances.In addition to ensure the absorption of nutrients,the intestinal also forms a barrier inside to protect the host from harmful substances.The gut microbiota plays an important role in maintaining intestinal homeostasis and regulating host metabolism,and liver diseases are often closely related to changes in gut bacterial composition or microecological imbalances.In this study,polystyrene microplastics(PS-MPs)and tetracycline hydrochloride(TCH)were used to evaluate the toxic effects of PS-MPs alone or co-exposed with TCH on the intestine and liver,respectively,in animal experiments(5-week-old ICR mice as model organisms)and in vitro cellular experiments(human hepatoma cell line Hep G2 cells as model organisms),in combination with the determination of PS-MPs characterization before and after TCH adsorption.The main research results are as follows:1)Firstly,the characterization of PS-MPs before and after adsorption of TCH showed that TCH did not affect the surface morphology of PS-MPs,but promoted the agglomeration effect of PS-MPs.Meanwhile,we also investigated the effects of continuous five-week exposure to PS-MPs and/or TCH on the health status of mice,and the results showed that low exposure doses of PS-MPs and TCH did not affect the normal physiological activities of mice.2)Secondly,this study investigated the pathological and functional injuries of different intestinal segments and the microbial disorder upon exposure to PS-MPs and/or TCH.The results show that both the PS-MPs and TCH altered the intestinal morphology and induced functional impairment.However,the PS-MPs primarily damaged the colon,while TCH mainly damaged the small intestine.Combined treatment evoked ameliorative adverse effect on the intestinal segments except for the ileum.Gut microbiota analysis revealed that PS-MPs and/or TCH decreased gut microbiota diversity,especially the PS-MPs.In addition,the PS-MPs and TCH affected the microflora metabolic processes,especially protein absorption and digestion.3)Finally,in vitro experiments,the toxic effects of PS-MPs and/or TCH on Hep G2 cells were investigated by AB,MTT,JC-1 and ROS methods and the contents of glucose and lactic acid in cells were determined.The results show that PS-MPs has no significant toxic effect on Hep G2 cells,while TCH reduces mitochondrial succinate dehydrogenase activity and glucose content in Hep G2 cells,improves mitochondrial membrane potential,and thus affects the function of Hep G2 cells.Compared with TCH alone exposure,PS-MPs and TCH combined exposure had improved effects on Hep G2 cells.