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 17ß-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.

CCN2 Mediates S1P-Induced Upregulation of COX2 Expression in Human Granulosa-Lutein Cells.

CCN1 and CCN2 are members of the CCN family and play essential roles in the regulation of multiple female reproductive functions, including ovulation. Cyclooxygenase-2 (COX2) is a critical mediator of ovulation and can be induced by sphingosine-1-phosphate (S1P) through the S1P1/3-mediated Yes-associated protein (YAP) signaling. However, it is unclear whether CCN1 or CCN2 can mediate S1P-induced upregulation of COX2 expression and increase in prostaglandin E2 (PGE2) production in human granulosa-lutein (hGL) cells. In the present study, we investigated the effects of S1P on the expressions of CCN1 and CCN2 in hGL cells. Additionally, we used a dual inhibition approach (siRNA-mediated silencing and small molecular inhibitors) to investigate the molecular mechanisms of S1P effects. Our results showed that S1P treatment significantly upregulated the expression of CCN1 and CCN2 in a concentration-dependent manner in hGL cells. Additionally, inhibition or silencing of S1P1, but not S1P3, completely abolished the S1P-induced upregulation of CCN2 expression. Furthermore, we demonstrated that S1P-induced nuclear translocation of YAP and inhibition or silencing of YAP completely abolished the S1P-induced upregulation of CCN1 and CCN2 expression. Notably, silencing of CCN2, but not CCN1, completely reversed the S1P-induced upregulation of COX2 expression and the increase in PGE2 production. Thus, CCN2 mediates the S1P-induced upregulation of COX2 expression through the S1P1-mediated signaling pathway in hGL cells. Our findings expand our understanding of the molecular mechanism underlying the S1P-mediated cellular activities in the human ovary.

Hippo pathway functions as a downstream effector of AKT signaling to regulate the activation of primordial follicles in mice.

Clarifying the molecular mechanisms by which primordial follicles are initiated is crucial for the prevention and treatment of female infertility and ovarian dysfunction. The Hippo pathway has been proven to have a spatiotemporal correlation with the size of the primordial follicle pool in mice in our previous work. But the role and underlying mechanisms of the Hippo pathway in primordial follicle activation remain unclear. Here, the localization and expression of the core components were examined in primordial follicles before and after activation. And the effects of the Hippo pathway on primordial follicle activation were determined by genetically manipulating yes-associated protein 1 (Yap1), the key transcriptional effector. Furthermore, an AKT specific inhibitor (MK2206) was added to determine the interaction between the Hippo pathway and AKT, an important signaling regulator of ovarian function. Results showed that the core components of the Hippo pathway were localized in both primordial and primary follicles and the expression levels of them changed significantly during the initiation of primordial follicles. Yap1 knockdown suppressed primordial follicle activation, while its overexpression led to the opposite trend. MK2206 downregulated the ratio of P-MST/MST1 and upregulated the ratio of P-YAP1/YAP1 significantly, whereas Yap1-treatment had no influence on AKT. In addition, YAP1 upregulation partially rescued the suppression of the primordial follicle activation induced by MK2206. Our findings revealed that the Hippo-YAP1 regulates primordial follicular activation, which is mediated by AKT signaling in mice, thus providing direct and new evidence to highlight the role of Hippo signaling in regulating ovarian follicles development.

[Signaling molecules and pathways involved in maintaining the quiescence of primordial follicles].

Reproductive lifespan in female mammals is related to the size of primordial follicles pool, which relies on the balance between activated and quiescent primordial follicles. Therefore, the molecular mechanisms of recruiting and maintaining quiescence of primordial follicles have become hot research topics recently. Multiple studies have shown that genetic mutations, local ovarian autocrine and paracrine factors, proto-oncogene and tumor-suppressor genes are involved in the maintenance of balance between quiescent and activated primordial follicles. In the present review, we summarize recent research progress of the important signaling molecules and pathways that maintain the quiescence of primordial follicles.