Polystyrene microplastics impair mouse oocyte maturation by interfering with fatty acid oxidation

Abstract Microplastics (MPs) represent a significant environmental pollutant and have raised considerable concern due to their tendency to accumulate in animals, plants, and humans, thereby posing potential health risks. In this study, female mice were exposed to different doses of polystyrene microplastics (PS-MPs) (0, 0.3, 3, and 30 mg/kg) via intragastric administration for 35 days to investigate their effects on female reproductive health. The results showed a significant reduction in first polar body extrusion (PBE) and glutathione (GSH) levels, accompanied by increased reactive oxygen species (ROS) levels in germinal vesicle (GV) stage oocytes in the 30 mg/kg group. Based on these findings, the 30 mg/kg dose was selected for subsequent reproductive toxicity assessments. Compared with the control group, oocytes from the PS-MPs treated group exhibited a significant increase in spindle abnormalities and lipid droplet accumulation. RNA sequencing and experimental validation in mouse oocytes demonstrated that PS-MPs exposure led to upregulation of SIRT4 protein expression and downregulation of genes associated with fatty acid oxidation. Treatment with BEC2, a CPT1A activator, partially reversed the inhibitory effects of PS-MPs on fatty acid oxidation and improved oocyte maturation. Further analyses revealed that PS-MPs exposure reduced HSPA1A protein expression, potentially contributing to the activation of endoplasmic reticulum (ER) stress in ovarian cells. In addition, PS-MP exposure significantly altered the expression of genes related to ovarian fibrosis, angiogenesis, and aging. Knockdown of Hspa1a in the mouse granulosa cell line KK1 reduced cell proliferation and viability, induced G2/M cell cycle arrest, and triggered ER stress. Collectively, these findings suggest that PS-MPs exposure may accelerate ovarian aging by disrupting protein homeostasis and impair oocyte maturation in mice by disrupting fatty acid oxidation.