The Combined Effects Of Polystyrene With Different Sizes And Cadmium On Kidney In Mice

Objective: The threat of nano-and microplastics(NMPs)to human health cannot be underestimated.The toxic effects of polystyrene(PS),one of the common polymers in plastic products,have been widely studied.Size is one of the important factors affecting the toxic effects on organisms.In the natural environment,when organisms are exposed to PS with different size,the combined toxic effects on organisms will be more complex.Cadmium(Cd)can be adsorbed by PS and interacted,which change their bioavailability and toxicity in vivo.The combined effects of PS with different sizes and cadmium will lead to different toxic outcome.Mammalian kidney is an important accumulative organ of PS and Cd,and the study of the combined exposure of PS and Cd on kidney needs to be clarified urgently.The purpose of this study is to clarify the combined effects of PS with different sizes and Cd on kidney in mice,and to explore the related mechanism of toxic effects,so as to provide a reference for clarifying the threat assessment of PS combined exposure to human health in real environment.Methods: In this study,100 nm PS,1μm PS and Cd were selected,and the surface and size of PS were characterized.Sixty-four Kunming male mice were randomly divided into 8groups with normal saline as control group:(1)control group(2)100nm PS(3)1μm PS(4)100nm PS+1μm PS(5)Cd(6)Cd+100nm PS(7)Cd+1μm PS(8)Cd+100nm PS+1μm PS.The concentration of PS was 100mg/kg bw by gavage,and the concentration of Cd was 5mg/kg bw by gavage.The dosage of each group was 10ml/kg/ day per mice.The final body weight of the mice,liver,heart,spleen,lung,kidney and other organs were weighed,and the organ coefficient was calculated.Serum urea nitrogen(BUN)and creatinine(SCR)were detected to evaluate the changes of renal function.Paraffin section was used to observe the pathological changes of kidney tissue.TUNEL staining was used to evaluate renal cell apoptosis.The redox status of renal tissue(SOD,T-AOC,GSH)was detected by kits.RT-PCR was used to detect the expression levels of apoptosis-related genes P53,Cyt-c,Caspase-3 and inflammation-related genes Caspase-1 and IL-1β.Western blot was used to detect the expression levels of mitochondrial apoptosis pathwayrelated proteins P53,Bax,Bcl-2,and Caspase-3,and inflammatory response related proteins ASC and IL-1β.Results: 1.PS characteristics: 100 nm PS and 1μm PS have regular shape,smooth surface and uniform size distribution.2.The combined effects of PS and Cd on the basic conditions of mice: compared with the Cd group,the body weight of mice in PS with different sizes and Cd combined group increased slowly(P<0.05),and the kidney coefficient was significantly increased(P<0.05).3.The combined effects of PS and Cd on kidney function:compared with PS alone group,BUN and SCR expression levels were significantly increased in PS combined group(P<0.05),and BUN and SCR expression levels were synergistic significantly caused by the three combined exposure(P<0.05).4.The combined effects of PS and Cd on the pathological changes of kidney tissue: compared with the PS alone group,the PS combined group caused more pathological changes in kidney.Compared with the Cd group,the Cd+100nm PS+1μm PS group caused renal interstitial inflammation and renal tubule vacuolation,the epithelial cell arrangement disorder was more serious,and the pathological area was wider.5.The combined effects of PS and Cd on apoptosis of mouse kidney cells: Compared with PS alone group,the apoptosis rate of cells in the PS combined group was significantly increased(P<0.05),and the apoptosis of cells in the Cd+100nm PS group was more serious than that in the Cd+1μm PS group(P<0.05),and the apoptosis of kidney cells was the most serious(P<0.05).6.The combined effects of PS and Cd on the redox status of kidney: The expression level of SOD in 100 nm PS group was significantly lower than that in 1μm PS group(P<0.05).The expression levels of T-AOC and GSH in PS combined group were decreased compared with that in PS alone group(P<0.05).The synergistic effect of Cd and PS combined with different sizes on SOD and GSH expression levels was significant(P<0.05).Compared with Cd+1μm PS,the expression level of SOD was significantly decreased(P<0.05),and showed a synergistic effect(P<0.05).7.The combined effects of PS and Cd on apoptosis and inflammation related genes m RNA expression of kidney cells: compared with PS alone group,m RNA expression levels of caspase-3,caspase-1 and IL-1β were increased in PS combined exposure group(P<0.05).The m RNA expression level of caspase-1 in Cd+100nm PS group was higher than that in Cd and Cd+1μm PS groups(P<0.05).Conclusion: 1.PS with different sizes induced different nephrotoxicity in mice,the degree of nephrotoxicity induced by 100 nm PS was more severe than that induced by 1μm PS.2.Combined exposure of PS with different sizes cause more serious kidney damage than PS with single size,showing combined effects.3.The combined of PS and Cd caused more serious kidney damage than single group,The combined effects of PS with different sizes and Cd on kidney was the strongest.