Objective To investigate the effects and potential mechanisms of polystyrene micro/nanoplastics(PS-MNPs)on testicular Sertoli cells.Methods Sixty male C57BL/6N mice(8 weeks old)were randomly divided into a control group(deionized water),a PS-NPs group[particle size of 20 nm,2.5 mg/(kg·d)],and a PS-MPs group[particle size of 5 μm,2.5 mg/(kg·d)],with 20 mice in each group.The corresponding agents were gavaged once daily for 6 months.HE staining was used to observe the histopathological and morphological changes in the testicular tissues.Immunohistochemistry of marker proteins was employed to evaluate the changes in the number of Sertoli cells.Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analyses were performed to identify functions and signaling pathways enriched in the testicular transcriptome.Mouse testicular Sertoli cell line TM4 was divided into a control group(deionized water),a 2.5NPs group(2.5 μg/mL),and a 2.5MPs group(2.5 μg/mL).All groups received continuous exposure through 130 cell passages.Cell viability and proliferative capacity were evaluated using CCK-8 assay and EdU incorporation,while cell migration was assessed using transwell and cell scratch assays.RT-qPCR and Western blotting were used to detect the changes in the expression of key molecules regulating mesenchymal phenotypic transformation(MPT)at mRNA and protein levels.Results Pathological analysis revealed that,when compared to the control group,PS-NPs and PS-MPs treatment resulted in extended spaces between testicular seminiferous tubules,loosely arranged spermatogenic cells,and enhanced vacuolization.Immunohistochemical analysis of marker proteins indicated a decreasing trend in the number of testicular Sertoli cells in the PS-NPs and PS-MPs groups than the control group,with the PS-NPs group having statistical significance(P<0.01).GO and KEGG enrichment analyses revealed that PS-MNPs exposure-related altered genes were significantly enriched in cell adhesion signaling pathways(P<0.05).PS-MPs exposure significantly inhibited the growth and migration ability of TM4 cells(P<0.05),but PS-NPs exposure had no such effect on cell growth but notably enhanced cell migration ability.PS-NPs exposure inhibited the expression levels of E-cadherin and ZO-1(P<0.01)and up-regulated the expression of N-cadherin and vimentin(P<0.01),and PS-MPs exposure led to significant up-regulation of vimentin(P<0.01)and down-regulation of E-cadherin,N-cadherin,and ZO-1(P<0.05).Both PS-MPs and PS-NPs exposure up-regulated the mRNA levels of Snail2,Twist1,and Zeb2(P<0.01).Conclusion Exposure of PS-MNPs leads to abnormal proliferation and migration of TM4 cells,induces decreases in cell-cell contacts among Sertoli cells and spermatogenic cells at all levels possibly through MPT,and thus results in testicular damage.

Objective To investigate whether long-term low-dose exposure to polystyrene microplastics(PS-MPs)induces ferroptosis in testicular Sertoli cells and then leads to testicular injury.Methods Forty 8-week-old male C57BL/6 mice were randomly divided into a control group(deionized water group)and a PS-MPs group[2.5 mg/(kg·d)],with 20 mice in each group.Corresponding agents were gavaged once a day for 12 consecutive months.HE staining and Prussian blue staining were used to detect histopathological damage and accumulation of ferrous ions in the testes.Electron transmission microscopy was employed to observe the mitochondrial morphology of testicular Sertoli cells.Mouse Sertoli cell line TM4 was divided into a Con group(standard culture)and an MPs group(2.5 μg/mL PS-MPs).After both groups underwent continuous exposure and passed up to the 100th generation,morphological changes were observed under the microscope;cell viability was detected with CCK8 assay,and production of reactive oxygen species(ROS)and mitochondrial membrane potential(MMP)were detected with a ROS probe and a mitochondrial membrane potential probe(JC-1),respectively.Flow cytometry,ferrous ion(Fe2+)kit and Western blotting were applied to detect cell apoptosis,intracellular iron ion content,and protein levels of key molecules of ferroptosis in tissues and cells.Results Long-term exposure to PS-MPs resulted in significantly reduced diameter and thickness of mouse varicocele(P<0.01),fewer testicular Sertoli cells(P<0.05),with characteristic ferroptosis alterations in the mitochondria,and increased accumulation of ferrous ions in testicular tissue.Exposure to PS-MPs down-regulated the key molecules of ferroptosis,glutathione peroxidase 4(GPX4)and ferritin light chain(FTL)when compared with the control group(P<0.05).In the cell model,long-term PS-MPs exposure led to morphological changes and decreased cell viability(P<0.05),more production of ROS(P<0.01),and decrease in MMP(P<0.05)of TM4 cells.The exposure had no effect on cell apoptosis,but elevated the intracellular content of ferric ions(P<0.01),and down-regulated GPX4 and FTL protein levels(P<0.05).Conclusion Long-term low-dose exposure to PS-MPs induces mitochondrial damage and oxidative stress in testicular Sertoli cells,activates the ferroptosis pathway,and ultimately leads to testicular injury in mice.