Melatonin Alleviates the Damage of Polystyrene Microplastics to Porcine Oocytes by Reducing Oxidative Stress and Mitochondrial Damage, and Regulating Autophagy and Apoptosis Levels

Polystyrene microplastics (PS-MPs) are microplastic particles produced during plastic manufacturing and environmental degradation, accumulating over time and entering ecosystems through various pathways, ultimately affecting organisms and inducing toxic effects. Current research on the impact of PS-MPs on mammalian oocyte quality, along with potential preventive mechanisms and strategies to mitigate toxicity, remains limited. This study investigates the effects of antioxidant melatonin on oocyte quality in the presence of PS-MPs, focusing on their influence on oocyte meiotic maturation and embryonic developmental potential. PS-MPs at a concentration of 30 μg/mL significantly impaired first polar body extrusion and reduced the success rate of parthenogenetic activation of mature oocytes in vitro. Furthermore, exposure to PS-MPs exacerbated oxidative stress, mitochondrial dysfunction, apoptosis, and autophagy impairment. Additionally, PS-MPs exposure led to a reduction in antioxidant gene expression and an increase in apoptosis-related gene expression in porcine oocytes. Immunofluorescence assays revealed that PS-MPs may induce oxidative stress, mitochondrial damage, and inflammation through the NF-KB/Nrf2/JNK MAPK signaling pathway crosstalk. Further investigation demonstrated that melatonin supplementation alleviated the toxic effects of PS-MPs exposure, offering potential as a therapeutic approach for mitigating PS-MP-induced reproductive toxicity and preserving oocyte quality.