Polystyrene nanoplastics induce apoptosis, autophagy, and steroidogenesis disruption in granulosa cells to reduce oocyte quality and fertility by inhibiting the PI3K/AKT pathway in female mice

Background: Nanoplastics (NPs) are emerging pollutants that pose risks to living organisms. Recent findings have unveiled the reproductive harm caused by polystyrene nanoparticles (PS-NPs) in female animals, yet the intricate mechanism remains incompletely understood. Under this research, we investigated whether sustained exposure to PS-NPs at certain concentrations in vivo can enter oocytes through the zona pellucida or through other routes that affect female reproduction.

Results: We show that PS-NPs disrupted ovarian functions and decreased oocyte quality, which may be a contributing factor to lower female fertility in mice. RNA sequencing of mouse ovaries illustrated that the PI3K-AKT signaling pathway emerged as the predominant environmental information processing pathway responding to PS-NPs. Western blotting results of ovaries in vivo and cells in vitro showed that PS-NPs deactivated PI3K-AKT signaling pathway by down-regulating the expression of PI3K and reducing AKT phosphorylation at the protein level, PI3K-AKT signaling pathway which was accompanied by the activation of autophagy and apoptosis and the disruption of steroidogenesis in granulosa cells. Since PS-NPs penetrate granulosa cells but not oocytes, we examined whether PS-NPs indirectly affect oocyte quality through granulosa cells using a granulosa cell-oocyte coculture system. Preincubation of granulosa cells with PS-NPs causes granulosa cell dysfunction, resulting in a decrease in the quality of the cocultured oocytes that can be reversed by the addition of 17β-estradiol.

Conclusions: This study provides findings on how PS-NPs impact ovarian function and include transcriptome sequencing analysis of ovarian tissue. The study demonstrates that PS-NPs impair oocyte quality by altering the functioning of ovarian granulosa cells. Therefore, it is necessary to focus on the research on the effects of PS-NPs on female reproduction and the related methods that may mitigate their toxicity.