Polystyrene microplastics induce liver toxicity and cytoskeleton alterations in female rats

Microplastics (MPs) are emerging environmental pollutants that have received increasing attention in recent years. However, data on their potential risks to mammalian species remain limited. In this study, female rats were exposed via oral gavage to pristine (PPS) and fluorescent polystyrene (FPS) particles (5 μm diameter) over four estrous cycles. FPS-MPs were detected in hepatic tissue (133 ± 35 particles), confirming their translocation. Exposure to PPS-MPs increased superoxide dismutase (SOD) (2.58-fold) and catalase (CAT) activity (1.36-fold), while reducing protein sulfhydryl levels (PSH) (0.35-fold), indicating oxidative stress. Histological analysis and quantitative assessment revealed significant alterations, including significant decrease in glycogen content (2.4- fold). Immunofluorescence analysis showed a pronounced increase in α-tubulin and a decrease in DAAM-1 signals, a formin protein essential for actin filament assembly and cytoskeletal organization, suggesting impaired cytoskeletal dynamics. These observations were further supported by molecular analyses, which showed α-tubulin overexpression (3.35-fold) and reduced DAAM-1 expression (0.5-fold). Our findings indicate that exposure to environmentally relevant concentrations of MPs induces early hepatocellular alterations, suggesting that oxidative stress and cytoskeletal remodeling may be central mechanisms underlying MP-induced hepatotoxicity. These findings should be interpreted with caution, as the study used only female rats, a single dose, particle size, and polymer type, with a short exposure duration, and it should be noted that FPS-MPs were used only to track distribution, whereas toxicity assessments were performed with non-fluorescent particles.