Toxic Effects Of Polystyrene Microplastics On Rat Liver

Objective:To determine the toxicity of Polystyrene microplastics（PS-MPs）exposured to rat s’livers;To investigate the mechanism of PS-MPs exposure on liver injury in rats,and to provide scientific basis for clarifying the toxic effect and mechanism of PS-MPs and preventing and treating liver injury caused by PS-MPs.Methods:A total of 48 SPF male Wistar rats aged 6 weeks were randomly divided into 4groups:control group,low dose group（0.5mg/kg/d）,medium dose group（5mg/kg/d）and high dose group（50mg/kg/d）after adaptive feeding for 1 week,with 12 rats in each group.Poisoning was administered by gavage once a day for 90 consecutive days.Low,medium and high dose groups were given the corresponding concentration of 0.5μm PS-MPs,and the control group was given the corresponding volume of distilled water.The rats were observed every day,and the changes of body weight,diet and water intake were recorded.After the last poisoning,the anesthetized rats were fasted for 24h,and the blood samples were collected from the heart and the serum was separated,and the liver tissue was used for reserve.HE staining was used to observe the histopathological changes of rat liver.The levels of IL-1 and TNF-αin serum and liver and IL-1βand IL-18 in liver were determined by ELISA.The activities of ALT and AST,MDA,SOD and GSH in serum and liver were detected by colorimetry.The ROS level and apoptosis of liver cells were determined by flow cytometry.The m RNA expression levels of apoptosis and pyroptosis related genes in rats’livers were detected by real-time RCR method.Western Blot was used to determine the expression levels of apoptosis and pyroptosis related proteins.IBM SPSS 24.0 software was used for statistical analysis,and the measurement normal data was expressed by?ss.One-way ANOVA analysis of variance was used for inter-group comparison,and LSD method was used for inter-group pairwise comparison.The test level wasα=0.05.Results:1.After PS-MPs exposured,hepatocyte swelling and hepatocyte cord arrangement disorder appeared in the liver of rats in the 0.5mg/kg/d and 5mg/kg/d groups,and hepatocyte boundaries were blurred and hepatocytes were granular degeneration in the liver tissue of rats in the 50mg/kg/d group.2.ALT activity in serum in 50mg/kg/d group was significantly higher than that in0.5mg/kg/d group,and ALT activity in the liver in 0.5mg/kg/d and 5mg/kg/d groups was significantly lower than that in control group（P<0.05）.AST activity in the serum in50mg/kg/d group was significantly higher than that in 0.5mg/kg/d and 5mg/kg/d groups,and AST in the liver activity was significantly lower than that in other groups（P<0.05）.3.The content of MDA in serum and liver of 5mg/kg/d group was significantly higher than that in control group and 0.5mg/kg/d group（P<0.05）.The SOD level in serum in 50mg/kg/d group was significantly lower than that in control group and5mg/kg/d group（P<0.05）.SOD in liver of rats in 0.5mg/kg/d and 5mg/kg/d groups was significantly lower than that in control group（P<0.05）,and that in 50mg/kg/d group was significantly higher than that in 0.5mg/kg/d and 5mg/kg/d groups（P<0.05）.GSH content in the liver of rats increased gradually with the increase of the dose,GSH content in the liver in 5mg/kg/d group was significantly higher than that of control group（P<0.05）,and GSH content in the liver in 50mg/kg/d group was significantly higher than that in other groups（P<0.05）.4.IL-1 level in the serum in 0.5mg/kg/d group was significantly higher than that in control group and 5mg/kg/d group（P<0.05）.The levels of IL-1βand IL-18 in liver of rats were firstly decreased and then increased with the dose increasing,and the level of IL-1βin serum of rats in 50mg/kg/d group was significantly higher than that in0.5mg/kg/d and 5mg/kg/d groups（P<0.05）.The level of IL-18 in liver in 5mg/kg/d group was significantly higher than that in control group（P<0.05）.5.The Bax m RNA expression level in liver of rats in 0.5mg/kg/d and 5mg/kg/d groups was significantly lower than that in control group（P<0.05）,and the Bax m RNA expression level in 50mg/kg/d group was significantly higher than that in 0.5mg/kg/d and 5mg/kg/d groups（P<0.05）.The expression level of Bax protein in 5mg/kg/d group was significantly higher than that in 0.5mg/kg/d and 50mg/kg/d groups.The expression level of Bcl₂ m RNA in 50mg/kg/d group was significantly higher than that in other groups（P<0.05）.6.The m RNA expression levels of Caspase-1 and GSDMD in 50mg/kg/d group were significantly higher than those in control group（P<0.05）.The protein expression level of GSDMD in 5mg/kg/d group was significantly higher than that in control group and0.5mg/kg/d group（P<0.05）.Conclusion:In this study,0.5μm PS-MPs was toxic to rats’livers.1.Polystyrene microplastics can cause hepatic cell swelling and hepatic cell cord arrangement disorder in rats’livers,and even fuzzy boundary of liver cells and hepatic cell granular degeneration.2.Polystyrene microplastics can increase the activity of ALT and AST in rats’livers and cause hepatic cell damage.3.Polystyrene microplastics can cause changes in oxidative stress indexes in serum and liver of rats,resulting in imbalance of oxidation and antioxidant effects in liver cells,and leading to oxidative stress response in liver of rats.4.Polystyrene microplastics can increase the levels of inflammatory factors in serum and liver of rats,leading to the inflammatory response of the liver of rats.5.Polystyrene microplastics can induce apoptosis and pyroptosis related genes and protein levels in rats’livers,and promote apoptosis and pyroptosis in liver cells,leading to liver injury in rats.