PPARγ/mTOR Regulates the Synthesis and Release of Prostaglandins in Ovine Trophoblast Cells in Early Pregnancy

SIMPLE SUMMARY: During early gestation, a series of prostaglandins are synthesized and secreted by the sheep’s conceptus. The ratio of PGE(2) to PGF(2α) is very important for embryo attachment. In this process, the expression level of PPARγ also begins to increase, and prostaglandin metabolites are natural endogenous ligands of PPARγ. Inhibition of PPARγ activity can enhance mTOR signaling. However, the precise roles of PPARγ/mTOR during this process are unknown. Here, we found that inhibiting PPARγ activity in trophoblastic cells disequilibrated their synthesis and secretion of prostaglandins, while blocking the mTOR pathway restored it to normal levels. Our results demonstrate that PPARγ/mTOR are likely to function in the synthesis of prostaglandins. These findings extend our understanding and may provide new insights into the mechanism of PPARγ/mTOR regulation of prostaglandin secretion in trophoblastic cells. ABSTRACT: Trophoblast cells synthesize and secrete prostaglandins (PGs), which are essential for ruminants in early gestation to recognize pregnancy. Hormones in the intrauterine environment play an important role in regulating PGs synthesis during implantation, but the underlying mechanism remains unclear. In this study, co-treatment of sheep trophoblast cells (STCs) with progesterone (P(4)), estradiol (E(2)), and interferon-tau (IFN-τ) increased the ratio of prostaglandin E2 (PGE(2)) to prostaglandin F2α (PGF(2α)) and upregulated peroxisome proliferator-activated receptor γ (PPARγ) expression, while inhibiting the mechanistic target of rapamycin (mTOR) pathway and activating cellular autophagy. Under hormone treatment, inhibition of PPARγ activity decreased the ratio of PGE(2)/PGF2α and cellular activity, while activating expression of the mTOR downstream marker—the phosphorylation of p70S6K (p-p70S6K). We also found that the PPARγ/mTOR pathway played an important role in regulating trophoblast cell function. Inhibition of the mTOR pathway by rapamycin increased the ratio of PGE(2)/PGF(2α) and decreased the expression of apoptosis-related proteins after inhibiting PPARγ activity. In conclusion, our findings provide new insights into the molecular mechanism of prostaglandin regulation of trophoblast cells in sheep during early pregnancy, indicating that the PPARγ/mTOR pathway plays an important role in PGs secretion and cell viability.